hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/ICY8BJ ------------------ When CPU 1 enters the nohz_full state, and the kworker on CPU 0 executes the function sched_tick_remote, holding the lock on CPU1's rq and triggering the warning WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3). This leads to the process of printing the warning message, where the console_sem semaphore is held. At this point, the print task on the CPU1's rq cannot acquire the console_sem and joins the wait queue, entering the UNINTERRUPTIBLE state. It waits for the console_sem to be released and then wakes up. After the task on CPU 0 releases the console_sem, it wakes up the waiting console_sem task. In try_to_wake_up, it attempts to acquire the lock on CPU1's rq again, resulting in a deadlock. The triggering scenario is as follows: CPU0 CPU1 ---- ---- sched_tick_remote WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3) report_bug con_write printk console_unlock do_con_write console_lock down(&console_sem) list_add_tail(&waiter.list, &sem->wait_list); up(&console_sem) wake_up_q(&wake_q) try_to_wake_up __task_rq_lock _raw_spin_lock This patch fixes the issue by deffering all printk console printing during the lock holding period. Fixes: d84b31313ef8 ("sched/isolation: Offload residual 1Hz scheduler tick") Signed-off-by: Wang Tao <wangtao554@huawei.com> --- kernel/sched/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7515d8f77194..4149f554debd 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3148,6 +3148,7 @@ static void sched_tick_remote(struct work_struct *work) goto out_unlock; update_rq_clock(rq); + printk_deferred_enter(); delta = rq_clock_task(rq) - curr->se.exec_start; /* @@ -3155,6 +3156,7 @@ static void sched_tick_remote(struct work_struct *work) * amount of time. */ WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3); + printk_deferred_exit(); curr->sched_class->task_tick(rq, curr, 0); out_unlock: -- 2.34.1